The game will feature detective-style investigation of monster "crime scenes". Geralt will need to discover which monster from his bestiary is responsible for murdering townsfolk, before he can track it down to its lair and slay it.
There will be a greater emphasis on preparation before monster battles. The developers imply that there will be multiple ways to prepare for each monster, one of them being learning its internal anatomical details (which kinda reminds me of the alien autopsies in X-COM). Another way in which The Witcher 3 will be returning to the roots of the Witcher concept is that monster hunting will be your primary source of income, and also your primary source of crafting materials and mutagens. There will be unique "boss" versions of monsters in the game, like in the original Witcher. The developers are quick to reassure that there won't be any arcade-style "epic" bosses like Witcher 2's infamous Kayran, though.

As long as it's not "get xth part of the crown in a dungeon you've visited already a thousand of times, got the book of arcane knowledge there and you still can't solve book's quest due to a bug" Skyrim annoying repeated quest, I'm good with it.

Sounds pretty cool. Where are these monster attacks happening though? Is Geralt finding mauled bodies in their homes? It's funny to think about some giant monster letting himself in the house, killing the person and silently returning to his lair without being seen . I'm sure they have thought this out better than that though. Sounds great really.

The more I think about this the more awesome it sounds. Investigating a crime scene and then hunting down the responsible monster in their lair is a pretty fun sounding concept, especially with it being an open-world to explore.

Crime scene investigation worked reasonably well in L.A. Noire, while the interrogation of suspects and witnesses was handled with less success. If you substitute the city of Los Angeles for a lot of wilderness with scattered villages and go for a less linear approach, it could be really good.

It's a bit more complicated Chien. One of the interesting things in Sapkowski's stories is that a reader (and Geralt) is often not sure just what (or who) the moster is.
Some "monsters" were made up by people but never existed in reality (nietopyrze). Some were considered "monsters" by people but not by Geralt. And than there were people whom he considered monsters. Last but not least there were "monsters" which Gerald considered as pure legends but which turned out to be real (golden dragon).

In any case, in Sapkowski's books, almost every time Geralt is faced with possible monster killing contract he starts with investigation about what sort of monster (if any) he might be dealing with.

I was a big fan of some of the investigation that you had to do in Witcher 1, particularly in the first half of the game. If they can recapture some of that for the monster investigations in Witcher 3 I will be quite happy.